Fruiting calyx bent back, papery, with a network of veins and the upper (adaxial) part swollen. Pod, 2-2.5 mm long, elliptic to oblong in outline, enclosed within the calyx or burr.

Seeds:

Dark brown, oval, ~1.5 mm long.

Roots:

Taproot. Has nitrogen fixing nodules on taproot and laterals.

Key Characters:

Annual herbLeaflets stalks are all the same length.Stipules entire, distinctly veined, partly joined to the petiole.Flower heads 4-10 mm across, not surrounded by bracts.Calyx 13 veined, hairy, gibbous with the adaxial part inflated and chartaceous.Calyx lobes of upper lip long, protruding from the fruiting calyx.Pod enclosed in the calyx.Adapted from Judy Wheeler, Flora of Perth.

Biology:

Life cycle:

Annual. Germinates autumn to spring. Flowers spring to early summer.

Physiology:

Has symbiotic rhizobia in nodules on the roots that fix atmospheric nitrogen.

Reproduction:

By seed.

Flowering times:

October to November in Perth.

Seed Biology and Germination:

Hard seeded.

Vegetative Propagules:

None.

Hybrids:

Commercial varieties are available.

Allelopathy:

Stubble can be allelopathic.

Population Dynamics and Dispersal:

Spread by seed.

Origin and History:

Europe, Mediterranean, Northern Africa, South Western Asia and the Middle East.Introduced as a pasture and hay species.

Loamy and clay loam red earths. Less common on sands, grey silts and heavy clays.

Plant Associations:

Capeweed, Annual Ryegrass.

Significance:

Beneficial:

Fodder.Fixes nitrogen.

Detrimental:

Weed of lawns roadsides and disturbed areas.Occasional weed of crops.

Toxicity:

Closely related species may cause photo sensitisation in cattle and clover disease in sheep and occasionally bloat. No field cases have been reported for this species, possibly because of it low occurrence.

Treatment:

Remove stock from infested areas if toxicity suspected.

Legislation:

None.

Management and Control:

Thresholds:

10-20/m2 is expected to cause 10% yield loss in cereals.Dicamba and sulfonylurea herbicides provide good control.

Eradication strategies:

Prevent seed set for 5 years.Exclude stock to prevent dispersal of seed and burrs.Hand pull isolated plants in winter before flowering. For small infestations and grass dominant areas an annual application of 10 mL Tordon®75-D in 10 L water in early winter gives excellent control of existing plants and has residual activity to control seedlings. In bushland, 200 g/ha Lontrel®750 or 50 g/ha Logran® applied in early winter provides reasonably selective control. Use 25 mL wetting agent plus 4 g Lontrel®750 or 1 g Logran® or 0.1 g metsulfuron(600g/L) or 0.1 g chlorsulfuron(750g/kg) in 10 L water for hand spraying when they are actively growing. Repeat annually for several years. Plant tall growing perennial species to reduce re-invasion. Clovers are relatively tolerant to glyphosate, grazing and mowing.

Shaftal clover (Trifolium resupinatum) is very similar to Woolly Clover (Trifolium tomentosum) but has a less hairy calyx ending in 2 obvious divergent lobes.Medics, Trefoils, Soursob, Large flowered Wood Sorrel or Four-o'clock, Oxalis spp.